Communication devices such as User Equipments (UE) are also known as e.g. mobile terminals, wireless terminals and/or mobile stations. User equipments are enabled to communicate wirelessly in a cellular communications network or wireless communication system, sometimes also referred to as a cellular radio system or cellular networks. The communication may be performed e.g. between two user equipments, between a user equipment and a regular telephone and/or between a user equipment and a server via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the cellular communications network.
User equipments may further be referred to as mobile telephones, cellular telephones, or laptops with wireless capability, just to mention some further examples. The user equipments in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the RAN, with another entity, such as another user equipment or a server.
The cellular communications network covers a geographical area which is divided into cell areas, wherein each cell area being served by a base station, e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. “eNB”, “eNodeB”, “NodeB”, “B node”, or BTS (Base Transceiver Station), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. One base station, situated on the base station site, may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the user equipments within range of the base stations.
In some RANs, several base stations may be connected, e.g. by landlines or microwave, to a radio network controller, e.g. a Radio Network Controller (RNC) in Universal Mobile Telecommunications System (UMTS), and/or to each other. The radio network controller, also sometimes termed a Base Station Controller (BSC) e.g. in GSM, may supervise and coordinate various activities of the plural base stations connected thereto. GSM is an abbreviation for Global System for Mobile Communications (originally: Groupe Spécial Mobile).
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), base stations, which may be referred to as eNodeBs or even eNBs, may be directly connected to one or more core networks.
UMTS is a third generation mobile communication system, which evolved from the GSM, and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for user equipments. The 3GPP has undertaken to evolve further the UTRAN and GSM based radio access network technologies.
In the context of this disclosure, the expression Downlink (DL) is used for the transmission path from the base station to the mobile station. The expression Uplink (UL) is used for the transmission path in the opposite direction i.e. from the mobile station to the base station.
3GPP LTE radio access standard has been written in order to support high bitrates and low latency both for uplink and downlink traffic. All data transmission is in LTE controlled by the radio base station. In order to support efficient uplink scheduling, a method has been defined to inform the base station of the buffer status of the UE. This method mainly comprises of buffer status reports (BSR) and scheduling request (SR). Both the BSR and the SR are sent from the UE to the base station. The UE triggers a BSR, this in turn trigger a SR to be sent unless a valid uplink data transmission resource is available, the base station receives the SR and give the UE a uplink data transmission resource, the UE then sends the BSR to the base station. A number of rules have been defined on when a UE should trigger a BSR, such as arrival of new data to an empty buffer. The BSR is sent on the physical uplink shared channel (PUSCH) like other data transmissions. Since a BSR transmission requires a valid uplink resource, SR has been defined as single bit information indicating to the base station that a BSR has been triggered in the UE. This may be performed by 1) a BSR is triggered in the UE, then 2) a SR message indicating that the BSR has been triggered is sent by the UE to the base station, and 3) then the triggered BSR is sent by the UE to the base station. The SR message is sent to the base station to request resources for the BSR. However, the base station may select to give a resource larger than just containing the BSR. The SR message may be transmitted either on a preconfigured semi-static configured periodic resource on the Physical Uplink Control Channel (PUCCH), referred to as Dedicated Scheduling Request (D-SR). It means that the base station may configure a resource, e.g. may send a message comprising index, periodicity and time offset, that shall be valid until a further notice is sent to the user equipment. There are some release rules, to release assigned recourses but in principle the UE keep the resource. If no such resource has been configured or configured resources have been released, SR is transmitted on the Random Access Channel (RACH). This SR may be referred to as Random Access Scheduling Request (RA-SR). The expression configured means here that the UE has a D-SR resource, configured over Radio Resource Control (RRC) and which is not released according to the release rules. The D-SR resource on the PUCCH uses a code division multiple access scheme to uniquely identify the user on a specific time/frequency resource. On each LTE uplink resource block pair, up to 36 unique code resources is available. A resource block pair is a 3GPP specific resource definition, it comprises two 0.5 ms/180 kHz time frequency blocks consecutive in time. On PUCCH they are not on the same frequency but frequency hopping is used so the first resource block is on one band-edge and the other is on the other band edge. It is up to the LTE base station, i.e. the eNodeB, to define the total size of the PUCCH and to divide the resources in time, frequency and code to each user, where the trade-off stands between short periodicities giving low latency but costing in larger overhead for control channels versus lower overhead but with longer delay. Typically an eNodeB may assign different UEs different periodicities dependent on service. D-SR resources are assigned, i.e. configured semi-statically using RRC signalling. The term semi-statically means that the UE has a D-SR resource, configured over RRC and not released according to the release rules. The RRC protocol is used in LTE/Evolved Universal Terrestrial Radio Access Network (E-UTRAN), and in Wideband Code Division Multiple Access (WCDMA) and handles the control plane signalling of Layer 3 between the UEs and the Universal Terrestrial Radio Access Network (UTRAN) or E-UTRAN. UTRAN is a collective term for the Node B's and Radio Network Controllers which make up the UMTS radio access network. RRC signalling is protected by both Hybrid Automatic Repeat reQuest (HARQ) and Radio Link Control (RLC) retransmission protocols, to be robust to packet loss in order to ensure that the same understanding of the configuration is valid in both the eNB and the UE. I.e all parameters set in the RRC message, for example the D-SR resource that this user equipment shall use.
The problem with the existing solution is that the UE need for D-SR resources may shift over time but the reconfiguration mechanism used, i.e. the procedure to send a further RRC message with a new configuration, is to slow and costly in terms of overhead in order to follow the variations.